﻿using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;

namespace WebAPI.Utils;

public class Captcha
{
    #region 生成验证码
    public static string CreateGraphic(string validateCode)
    {
        var image = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), 22);

        var g = Graphics.FromImage(image);

        try
        {
            //生成随机生成器
            var random = new Random();

            //清空图片背景色
            g.Clear(Color.White);

            //画图片的干扰线
            for (var i = 0; i < 25; i++)
            {
                var x1 = random.Next(image.Width);
                var x2 = random.Next(image.Width);
                var y1 = random.Next(image.Height);
                var y2 = random.Next(image.Height);
                g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
            }

            var font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic));
            var brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),

            Color.Blue, Color.Red, 1.2f, true);

            g.DrawString(validateCode, font, brush, 3, 2);

            //画图片的前景干扰点
            for (var i = 0; i < 100; i++)
            {
                var x = random.Next(image.Width);
                var y = random.Next(image.Height);
                image.SetPixel(x, y, Color.FromArgb(random.Next()));
            }

            //画图片的边框线
            g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

            //保存图片数据
            var stream = new MemoryStream();

            image.Save(stream, ImageFormat.Jpeg);

            //输出图片流
            return Convert.ToBase64String(stream.ToArray());
        }
        finally
        {
            g.Dispose();
            image.Dispose();
        }
    }

    // 生成CODE
    public static string CreateCode(int length)
    {
        var randMembers = new int[length];

        var validateNums = new int[length];

        var validateNumberStr = "";

        //生成起始序列值
        var seekSeek = unchecked((int)DateTime.Now.Ticks);

        var seekRand = new Random(seekSeek);

        var beginSeek = seekRand.Next(0, int.MaxValue - length * 10000);

        var seeks = new int[length];

        for (var i = 0; i < length; i++)
        {
            beginSeek += 10000;
            seeks[i] = beginSeek;
        }

        //生成随机数字
        for (var i = 0; i < length; i++)
        {
            var rand = new Random(seeks[i]);
            var minValue = 1 * (int)Math.Pow(10, length);
            randMembers[i] = rand.Next(minValue, int.MaxValue);
        }

        //抽取随机数字
        for (var i = 0; i < length; i++)
        {
            var numStr = randMembers[i].ToString();
            var numLength = numStr.Length;
            var rand = new Random();
            var numPosition = rand.Next(0, numLength - 1);
            validateNums[i] = int.Parse(numStr.Substring(numPosition, 1));
        }

        //生成验证码
        for (var i = 0; i < length; i++)
        {
            validateNumberStr += validateNums[i].ToString();
        }
        return validateNumberStr;
    }
    #endregion
}